A fundamental goal of automotive heating, ventilating, and air conditioning (HVAC) systems is to make vehicle occupants comfortable. To achieve this goal, it is important that the design of the control system that establishes cabin conditions takes into account the relationship between comfort and the variables that affect comfort. Human comfort is a complex reaction, involving physical, biological, and psychological responses to the given conditions. Because of this complexity, the engineer must consider many variables and their possible interaction in the design strategy of such a control system or controller.
In addition to the current difficulties, new vehicle lines create additional problems that are not easy to overcome. The reduction in interior and under hood package space in current vehicle designs has caused the transfer function for discharge temperature to be even more nonlinear, especially when operating at the extremes of ambient temperature.
It is often desirable to adapt a control strategy to a customer's or driver's preferences as well as the detection of special conditions thereby changing the response of the HVAC system.
The U.S. Pat. No. to Hara et al. 5,078,316 discloses computer controlled temperature regulation of an automobile in which the user's request modifies the automatic temperature control The computer receives input of ambient temperature, cabin temperature, insulation temperature and a cabin temperature setting. User modification signals are also inputted and the automatic temperature control is modified in response to the user signal.